Many times when you see an amulet (taweez) you will find it has knots in the string. This is a form of magic in and of itself, which is separate to the actual amulet. It is vital to open the knots.
How does a magician blow on knots? Firstly, he makes the knots and then he calls the names of the devils and then blows over them. As he does this, he tightens the knots. He continues to do this over each knot, calling upon the devils as he goes.
How to break these knots? Recite sura falaq and sura nas and then blow on the knot and then open it. Do this for each knot. If the knot is too tight then use a blade to cut the knot instead of opening it – but recite over it first. Ensure that all knots are either cut or untied. You can then leave the string in a bowl of water that has been recited over for about an hour before burning it.